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Section 14-1
Remote I/O Communications Characteristics
First, the Network is divided into two groups: Master A and the Slaves in remote
I/O communications with it and Master B and the Slaves in remote I/O communications with it.
Slave A
Group A
Group B
Master A
Master B
Slave B
Slave C
Slaves in remote I/O communications with Master A
Note
Slave D
Slave E
Slave F
Slaves in remote I/O communications with Master B
Although in the above diagram the Slaves are separated into two groups for convenience, the actual physical positions in the Network are irrelevant.
Next, we can refer to the previous equations and calculate the communications
cycle time for each group as if they were separate Networks.
Group B
Group A
Master B
Master A
Slave A
Slave B
Slave C
Group A communications
cycle time: TRM-A
Slave D
Slave E
Slave F
Group A communications
cycle time: TRM-B
In Networks with two Masters, the communications cycle time for the entire Network will be the sum of the communications cycle times for the groups.
TRM = TRM-A + TRM-B
Although this example shows only two Masters in the Network, the total communications cycle time for any Network can be calculated by dividing it into groups
and adding the communications cycle times of all groups.
14-1-4 System Startup Time
This section describes the system startup time for a Network operating with the
scan list enabled. The system startup time is the delay from the time that the
Master Unit is turned ON until remote I/O communications begin. Here, we assume that the scan list is enabled and that remote I/O communications are set to
start automatically at startup.
System Startup Times
The following table shows the system startup times for two cases. In the first
case, the Master Unit starts up just after all of the Slaves’ power supplies are
turned ON. In the second case, the Master Unit is restarted while communications are in progress.
Case
Slave’s indicator status
The Master is started just
after Slave startup.
Just the Master is restarted.
The NS indicator is OFF or
flashing green.
The NS indicator is flashes
red while the Master is OFF.
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Just the Slaves are
restarted.
System startup time
6 seconds
8 seconds
10 seconds
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